Generally, the present invention is a suspension member that is intended to be used mainly on the front end of a vehicle to prevent an increase in mass at welded portions.
Specifically, the present invention is a suspension member for connecting a suspension device to a vehicle body that comprises a pair of side members that extend in the longitudinal direction of the vehicle body and are provided symmetrically relative to the center in the transverse direction of the vehicle body, and at least one cross member extending in the transverse direction of the vehicle body and connecting the pair of longitudinal side members at an interval therebetween. Press-molding is carried out thereon after the flat plate-like side members and the cross members are butt-welded, and then the upper panel and lower panel are structured, and finally the upper panel and the lower panel are welded.
Further, in the suspension member, the edges of the longitudinal side members that comprise the upper panel may project towards the inner side of the vehicle body in the transverse direction respectively so as to form a square U-shape that opens to the inner side in the transverse direction of the vehicle body in plan view, and the projected portions may be welded to the cross members that comprise the upper panel in a butt joint.
Presently known suspension members present a problem in that the side members and the cross members that are press-molded in advance are welded together, and therefore these members are overlapped and the entire mass of the suspension member is increased. Nonetheless, in the present suspension member, in order to eliminate the overlapped members, after the flat plate-like side member and the flat plate-like cross members are butt-welded, they are press-molded so as to prepare the upper panel and lower panel.
In addition, in conventional suspension members, the joint portions of the cross member that are press-molded in advance are welded together with the side members that are also press-molded in advance, and stress may concentrate around the welded portions of the cross members relative to the side members. Contrary to this, in the present suspension member the flat plate-like members are butt-welded prior to the press-molding, thereby reducing such a concentration of stress. Consequently, the fatigue strength of the welded portion can be increased and the reliability of the suspension member can be improved.
In addition, where an upper panel has an opening facing downwardly so that the upper panel has an approximately square U-shape in a cross-sectional view, and a lower panel has a flat plate-like shape, the suspension member is deformed in a buckling V-shape downwardly when viewed from the transverse direction of the vehicle body should the vehicle experience a frontal collision. In such a case, the reaction force required during the collision is mainly carried by the side member portions of the side members of the upper panel. Thus, the reaction force borne by the lower panel can be reduced.
Since the rigidity of the upper panel is significant, it is difficult to adopt such a structure because, in the conventional technology, its mass increases as its rigidity is increased. On the other hand, in the present suspension member it is possible to prevent increase of the mass thereof and to adopt such a structure.
Furthermore, when the side members that have been press-molded in advance are welded with the cross members that have been press-molded in advance, a joint portion of the side portion of the side member and an edge of the cross member form a corner of the suspension member, and therefore stress is easily concentrated around the welded portion of the side member and the cross member. In such cases, although the reliability of the suspension member can be improved by increasing the fatigue strength of the welded portion by enlarging the joint portion that is formed at the edge of the cross member, it is not desirable to do so because the weight of the suspension member is increased.
In contrast, the present suspension member may be configured so that the edges of the longitudinal side members that comprise the upper panel project towards the inner side in the transverse direction of the vehicle body, so that the side members have a square U-shape that opens to the inner side in the transverse direction of the vehicle body in plan view, and the edge portions of the longitudinal direction, which projected towards the inner side in the transverse direction of the vehicle body, are butt-welded to the cross members that comprise the upper panel. And thus, the welded portions can be configured by avoiding the corners of the double crossed suspension member. Consequently, the welded portions can be located at portions other than the corners where the stress can be easily concentrated, whereby the reliability of the suspension member can be increased.
The foregoing remarks have outlined rather broadly certain features and technical advantages in order that the following detailed description may be better understood. Additional features and advantages will be described hereinafter.